Method

Now go down the hole; you will find many bears here. Run past them or try to kill them and do not get trapped. The cave splits in two ways: Choose the southern path. There's a small narrow passage, stand there if you are planning to kill the bears, so only that two can attack you at any given time. Do not use the Small Health Potions yet. At the end, there's a pool of water and a hole, open it with your Shovel and go down.

Here, it might be advisable to eat food and wait to have full HP. Now use your Scythe to cut the Wheat.

Take these, and do not wait for your HP to fill back up, return quickly to the entrance instead, you will save potions doing so. If you do it fast enough you will need only 2 Small Health Potions and some food. If you are level 7 or higher you can finish this quest without using any potions, just get there and loot the dragon corpse, wait till full hp and get out.